1. Field of the Invention
The present invention relates to a light emitting element housing package.
2. Description of the Related Art
In order to enhance efficiency in extracting light from a light emitting element, a light emitting element housing package that houses an optical semiconductor light emitting element, such as an LED, has demanded a technique for hindering a wiring pattern from absorbing light from the light emitting element.
For instance, a proposed technique is for making a thin silver film exhibiting a high reflectance on a surface of a wiring pattern. However, a silver thin film is likely to cause a problem, like migration or oxidative corrosion, thereby raising a problem of low reliability (see Patent Document 1) and expensiveness.
Accordingly, a technique for forming a white resist layer exhibiting high reflectance on a surface of a wiring pattern has already been proposed as described in connection with Patent Document 2.
Patent Document 1: JP-A-2009-135536
Patent Document 2: JP-A-2007-201171
Under the technique described in connection with Patent Document 2, a synthetic resin that is a base material of a white resist layer undergoes aged deterioration because of heat and light. Since the white resist layer is likely to undergo yellow discoloration, the layer encounters difficulty in maintaining a white color for a long period of time. For this reason, there also arises a problem of efficiency in extracting light from a light emitting element being deteriorated with age.